1. Field of the Invention
The present invention is directed toward differentials, in general, and more specifically, to a differential having torque proportioning capabilities.
2. Description of the Related Art
A differential is a component of an axle assembly and is used to couple a pair of rotating half shafts which make up a portion of the axle assembly. The differential is driven by the drive shaft via a pinion gear that meshes with a ring gear on the differential. In automotive applications, the differential allows the tires mounted at either end of an axle assembly to rotate at different speeds. This becomes important, for example, when the vehicle is turning. The outer tire travels over an arc of greater distance than the inner tire. Thus, the outer tire must rotate at faster speeds than the inner tire to compensate for the greater distance travelled.
Differentials include a gear set that allows for this relative rotation. However, when one tire is supported on a slippery surface, such as ice or mud, and the other is solidly supported, such as on dry pavement, an “open” differential gear set acts to transfer all power to the tires supported on the slippery surface. In this case, the tire on the slippery surface will spin and the tire on the dry pavement will not. Under these circumstances, the vehicle having an open differential can effectively become immobilized. Thus, it is known in the art to have differentials that function to transfer the torque from the slipping tire to the tire that is solidly supported. In this way, the vehicle is able to employ the traction at the solidly supported tire to move the vehicle.
There are a number of differential mechanisms that are known in the related art for use in distributing torque between the output shafts. One such differential employs a gear case having a pair of output or side gears that are rotatably supported within the gear case and fixed to respective ones of the output shafts that interconnect the differential with each tire driven by an associated axle. A plurality of pinion gears are also rotatably supported in the gear case. In the event of a differential in torque required at the tires—such as when one tire is slipping and the other tire is solidly supported when driving forward—the gear case, pinions and side gears cooperate to deliver a greater proportion of the torque to the solidly supported tire. In this way, the differential acts to automatically deliver more torque to the tire that needs it.
While torque proportioning differentials of the type generally known in the related art have worked well for their intended purposes, there is a constant need to improve the efficiency of their operation, to reduce losses due to mechanical interaction and increase the torque delivered via the differential to the output shafts. The present invention is directed toward increasing the efficiencies of torque proportioning differentials.